KIDNEY ALLOCATION SYSTEM FOR TRANSPLANTATION FROM DECEASED DONORS
The new kidney allocation system (KAS) went into effect in December, 2014. This was initiated by the United Network of Organ Sharing (UNOS), which is the nation’s transplant system, also known as the Organ Procurement and Transplantation Network (OPTN).
This new system will better match kidneys and donors based on new discoveries and data that is available currently. This involves creating a new classification system for kidneys and the patients or candidates who are waiting for those kidneys to become available.
How are kidneys classified?
Each kidney that is available for transplant now has a Kidney Donor Profile Index (KDPI). This is a percentage score between zero to 100 percent. It helps calculate how long a kidney is likely to function when compared to other kidneys. For example, a KDPI score of 20 percent means that the kidney is likely to function longer than 80 % of other available kidneys. In other words, the lower the percentage score, the better the quality of the kidney.
How is the KDPI score calculated?
This score is calculated by using certain facts from the donor. These include:
e) Whether the donor died from loss of brain function or heart function
f) Stroke as a cause for death
g) History of high blood pressure in the donor
h) History of diabetes in the donor
i) Whether the donor had hepatitis C
j) Serum creatinine
How are transplant candidates classified?
Each candidate has an individual Estimated Post-Transplant Survival (EPTS) score. This is a percentage score between zero to 100 percent. This score calculates how long the candidate on the wait list will need a functioning kidney transplant compared with other wait list candidates. For example, a candidate with an EPTS score of 20 percent is likely going to need a kidney longer than 80 % of other candidates. This score is calculated by the listing transplant center.
How is the EPTS score calculated?
This score is calculated by looking at certain candidate facts. These are:
b) Length of time spent on dialysis
c) Any previous organ transplants?
d) Current diagnosis of diabetes?
How are KDPI and EPTS scores used to allocate kidneys?
The kidneys with a KDPI of 20 percent- those that are expected to last the longest, are offered to candidates with an EPTS score of 20 percent or less- those who are expected to need the transplant the longest.
If an organ with a KDPI score of 20 percent or less is not accepted for a lower EPTS patient, they are then offered to any other person who would match, regardless of their EPTS score.
Kidneys with a high KDPI score are expected to last for a shorter period of time and are offered to candidates who are not able to stay on dialysis for a long time.
Kidneys with KDPI score of 85 percent or greater are offered first to a wider area of the country than other kidneys so that they are used as quickly as possible.
Children and teenagers receive priority for kidneys with a KDPI score of 35 percent or below.
How does the new system help patients who are hard to match?
Patients with blood type B and those with pre-existing antibodies (either because of previous transplants, pregnancy or blood transfusions) have been found to be hard to match and sometimes have to wait for years before they can get a suitable kidney. For a patient with blood type B, certain donors with blood type A have a “subtype” that allows them to donate to the type B candidates.
In both these instances, the candidates are given priority in the new KAS.